Conventionally, industrial food processors, such as meat grinders, are used to process meat into the consistency of sausage meat or burger meat, for example.
As shown in prior art FIGS. 1a and 1b, an industrial food processor generally comprises a steel rotary knife 10 mounted coaxially between a first perforated disc 12 and a second perforated disc 14 that are also made of steel. The discs 12 and 14 are fixed within a tubular housing (not shown). The knife 10 is rotatable about an axis of the food processor. A diameter of the knife 10 is smaller than a diameter of the discs 12 and 14.
The knife 10 comprises a central aperture 16, a hub 18, and eight arms 20 extending outwards from the hub 18. The central aperture 16 is adapted to receive a driveshaft (not shown). In use, the driveshaft rotates about the axis of rotation in order to rotate the knife 10.
The discs 12 and 14 comprise circular central apertures 22 and 24 respectively, entry surfaces 26 and 30 respectively, and exit surfaces 28 and 32 respectively. In use, the driveshaft may rotate freely relative to the discs 12 and 14 within the circular central apertures 22 and 24. The discs 12 and 14 further comprise a plurality of holes 34 and 36 respectively. The holes 34 and 36 extend through the discs 12 and 14 in a direction parallel to the axis of rotation of the knife 10. The holes 34 in the first disc 12 are larger than the holes 36 in the second disc 14.
The prior art knife 10 will now be described in more detail with reference to FIG. 2.
Each arm 20 of the knife 10 has respective first and second ends 40 and 42 respectively, the first end 40 being free and the second end 42 being connected to the hub 18 by means of a substantially annular portion 44 which surrounds the hub 18. A dimension of the annular portion 44 in the axial direction is less than that of the hub 18 such that the hub 18 protrudes axially from the annular portion 44.
Each arm 20 comprises a respective blade 46 that is substantially V-shaped in profile when viewed from the first end 40 of the arm 20. An axial dimension of each blade 46 is greater than the axial dimension of the annular portion 44 such that the blades 46 also protrude axially from the annular portion 44.
Each blade 46 comprises two planar surfaces 48 and 50 forming the V-shaped profile and two disc-engaging surfaces 52 and 54 that are perpendicular to the axis of rotation. The disc-engaging surfaces 52 and 54 and the planar surfaces 48 and 50 are arranged to have a substantially W-shaped profile when viewed from the first end 40 of the arm 20. Serrations 56 are provided in the blade 46 along an edge 60 joining the planar surface 48 with the disc-engaging surface 52. Similarly, serrations 58 are provided in the blade 46 along an edge 62 joining the planar surface 50 with the disc-engaging surface 54.
Referring back to FIGS. 1a and 1b, in use, meat, for example, is fed through the food processor in the direction shown by arrow X. The meat is fed through the food processor using, for example, a feed auger (not shown) which also rotates about the axis of rotation. The driveshaft rotates the knife 10 in the direction shown by arrow Y such that the V-shaped blades 46 are on the forward edge of the arms 20 with the V-shaped profile pointing rearwardly with respect to the direction of rotation.
As shown in FIG. 1a, the disc-engaging surface 54 rotates flush with the exit surface 28 of the first disc 12, and the disc-engaging surface 52 rotates flush with the entry surface 30 of the second disc 14. Thus, there is friction between the knife 10 and the discs 12 and 14. This reduces the efficiency of the food processor.
As the meat emerges from the holes 34 in the exit surface 28 of the first disc 12, the blades 46 of the knife 10 cut the meat as the knife 10 rotates. More specifically, the meat is cut by a scissor action between edges of the serrations 58 and edges of the holes 34.
The meat continues to be forced through the food processor by the feed auger in direction X. Inevitably, some meat escapes around the first ends 40 of the knife arms 20 due to the reduced diameter of the knife 10 compared to that of the discs 12 and 14. This reduces the efficiency of the food processor.
Eventually, the meat reaches the second disc 14 within range of an arm 20. As the meat enters the holes 36 in the entry surface 30 of the second disc 14, the blades 46 of the knife 10 cut the meat for a second time as the knife 10 rotates. More specifically, the meat is cut by a scissor action between edges of the serrations 56 and edges of the holes 36.
The processed meat is collected when it emerges from the holes 36 in the exit surface 32 of the second disc 14.
The amount of meat which can be processed by an industrial food processor in a given time is of key importance. The present invention seeks to provide an improved rotary knife which enables more efficient operation of a cutting apparatus such as an industrial food processor.